This invention relates generally to the fabrication of a nitrogen-doped gallium phosphide layer by vapor phase epitaxial growth, and more particularly to a method of producing such a layer which is substantially devoid of crystal defects and hence serves for giving a p-n junction of improved characteristics.
It is a well known and significant problem in the art of semiconductors that an epitaxial layer grown from a vapor phase involves frequently certain defects in its crystal. The defects are responsible for unsatisfactory characteristics of the junctions or semiconductor devices based on the epitaxial layer. Accordingly, various techniques have been proposed to form defectless epitaxial layers, but the results have been dissimilar depending on the semiconductor material.
Gallium phosphide is one of the materials for which the problem of such crystal defects is still unsolved. When a green-light-emitting GaP diode is produced by initially forming a nitrogen-doped n-type GaP epitaxial layer from a vapor phase and thereafter fabricating a p-n junction by diffusing zinc into the surface region of the n-type layer, the luminous efficiency of the diode is not so high as one of the similar diode produced by a solution growth method. The inferiority of the vapor growth product is considered to be attributable to crystal defects formed during doping and resulting strains in the epitaxial layer. Such defects and strains may also be created by the influence of the substrate.